This invention relates to devices for detecting infrared radiation (abbreviated to IR) in which the IR detector proper is constituted by one or a number of photoelectric detecting elements, said detector being cooled and supported by a cooling device. The IR detector is adapted to the prescribed spectral operating band and is usually positioned at the focus of a receiving optical system.
In addition to the cooling device, provision must be made for adjustment of the angle of view, or aperture of the detector, to the necessary value in order to limit as far as possible the continuous value of the detected current resulting from the observed background with a view to optimizing the detection signal-to-noise ratio. An optical aperture of the detector which exceeds the useful aperture of the collecting optical system results in an increase in the parasitic background current and consequently in the detected noise.